In the woodworking industry and elsewhere, it has long been a practice to drill a hole into a substrait (e.g. wood) where the end of the drilled hole is formed with a countersink (i.e. a frusto conical recess). This is commonly done to provide a pre-drilled hole for a screw having a countersunk head.
One method of accomplishing this is simply to drill the cylindrical drilled hole, and follow this by a second operation where the countersink forming member (i.e. one having a frusto conical cutting edge) is provided with a forwardly extending cylindrical shaped locating member to act as a locating member or pilot member. Then the pilot member is inserted into the hole (which is a pilot hole) to locate the countersink cutting member to form the centered countersunk recess at the top of the drill hole.
It has also been known in the prior art to provide a single drill and countersink assembly to accomplish this same task in one operation. This is done by providing first an elongate generally cylindrical drill member having three parts. First, there is the end drill tip; second a fluted shank portion; and third, an end mounting cylindrical section which can fit into the chuck of a drill. There is then provided a second countersink member which has a forward end at which there is a frusto conically shaped countersink cutting head. This countersink member is formed with a cylindrical through hole adapted to engage the fluted shank portion of the drill member. The drill member is inserted into the central opening in the countersink member to a depth so that the drilled portion extends beyond the countersink member to the appropriate depth. Then a set screw is inserted into a laterally threaded opening of the countersink member to bear against the fluted shank of the drill member to hold the drill member in place relative to the countersink member.
Also, a search of the patent literature has disclosed a number of U.S. patents, these being the following:
U.S. Pat. No. 3,794,438 (Knutson) discloses a drill member 1 having a shank, and there are two separate countersink elements 2 which fit in side by side relationship against the shank of the drill. These two countersink members 2 are pressed inwardly against the shank by means of a tightening member having a bottom section 4a with a frusto-conical surface that engages the frusto-conical surfaces of the members 2. Then there is a top section 5 having exterior threads which engages internal threads of the bottom section 4a. Thus, as the member 5 is threaded into the member 4a, the frusto-conical surface of the member 4a presses the two countersink sections 2 together.
U.S. Pat. No. 2,918,954 (Miller) discloses a drill member 40 which is inserted into an intermediate member 30 and held there by means of a set screw 42. The intermediate member 30 is in turn held in a shank 12 by means of another set screw 34.
U.S. Pat. No. 2,705,515 (Walker) shows a drill with a burnishing attachment. The drill 70 is secured by a set screw 72 in an adapted 71.
U.S. Pat. No. 2,486,363 (Purvis) shows a drill which fits within a center opening in a cleaning member C having bristles 10. A set screw 18 engages the shank portion 7 of the drill to hold in the cleaning member C.
U.S. Pat. No. 1,479,325 (Schubnel) shows a chuck where there is a drill 6 held by jaws 8 that have countersink-like cutting edges 9 at the lower ends thereof. The chuck body 7 has at the lower end an interior frusto-conical surface to grasp the jaws 8. There is a nut 18 which engages the chuck body the block 17 downwardly to in turn move the jaws 8 downwardly and into clamping relationship.
U.S. Pat. No. 1,229,565 (Ahlgren) shows a drill and countersink assembly where the countersink member 1 has upwardly extending arms formed by longitudinal splits 5 in the upper portion of the shank 3. The countersink member 1, with the drill being mounted therein is held by what appears to be a conventional chuck so as to press the upper arms 3 inwardly to grasp the drill.
U.S. Pat. No. 631,572 (Judson) shows what is called a reaming attachment for a bit, and this comprises a tubular reaming attachment which fits over a drill, with this being held in place by a set screw.
U.S. Pat. No. 332,308 (Valentine) shows a drill held in a countersink member with resilient arms to hold the drill.